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Lloyd Fournier
Chat_177 - Security Is Just a Hard Problem with Lloyd Fournier
- Frostsnap rethinks multisig using Shamir secret sharing, keeping key shares separate on devices that never reconstruct the private key in a single location; instead, devices produce signature shares that combine on-chain into a single signature. - The Coldcard entropy vulnerability exposed fundamental weaknesses in RNG implementation: weak fallback randomness (Yasmurang), compiler flags that disabled the hardware TRNG, and layers of obfuscation that made the bug extremely difficult to detect even with AI code analysis. - BLS signatures eliminate the need for randomness during signing by using pairing operations and group elements instead of field scalars, making them deterministic yet cryptographically secure—a major advantage over current ECDSA for hardware wallet security. - Dark Skippy attack demonstrates that even air-gapped hardware wallets with user-chosen seeds are vulnerable at signing time: a malicious device can leak seed words by embedding them in transaction signatures. - Hardware wallet manufacturers are inherently trusted third parties for entropy generation and signing; true security requires either offline randomness contribution (like a phone or laptop) or alternative cryptography that eliminates signing randomness entirely. - Quantum computing risk remains speculative and early-stage; proposed safeguards include taproot quantum-leaf backups triggered by a "quantum canary" challenge (breaking a smaller elliptic curve) rather than preemptive migration to quantum-resistant addresses.
The Coldcard Disaster: Everything You Need to Know | Lloyd Fournier & Nick Farrow
- A catastrophic Coldcard vulnerability in randomness generation affected approximately 1,200 wallets and nearly 2,000 Bitcoin, exposing years of stacking by users who followed best practices like self-custody. - The bug stemmed from Coldcard's use of the non-cryptographic Yasmarang RNG layered on top of device entropy, compressing the effective entropy to just 20–40 bits instead of 256 bits required for security. - An AI model (Grok/Claude/Kimmy-K3) discovered and exploited the vulnerability; multiple human reviewers, security audits, and safeguards all failed to catch five years of weak randomness. - Dark Skippy is a two-signature attack where a malicious device can leak a seed phrase through transaction nonces, demonstrating that hardware wallets remain trusted third parties regardless of air-gapping or entropy controls. - Distributed key generation and threshold signatures (Frost) used by Frostsnap eliminate single points of failure in randomness and remove the need for descriptor backups, improving recovery and inheritance. - The community debate now centers on whether users should roll dice, use multiple devices from different manufacturers, or accept that single-sig custody may require fundamental rethinking.